This invention relates to a fluid handling system for a dishwasher, and more particularly to a fluid handling system for a countertop dishwasher.
Fluid handling systems for dishwashers are known. U.S. Pat. No. 2,621,666 discloses a dishwashing machine which utilizes two separated chambers for containing washing fluid and rinsing fluid, respectively. The fluid is pumped into the wash chamber at appropriate times by the wash pump and the rinse pump. Water is drained from the dishwasher trough water vessel by siphon.
U.S Pat. No. 4,776,359 discloses a glass-washing machine having a control module which includes a pump/motor assembly disposed in a sump. A drain valve solenoid operates a drain valve for draining the sump at the appropriate time.
U.S Pat. No. 4,150,680, assigned to the assignee of the present invention, discloses a dishwasher which includes a single pump which acts both as a wash pump and a drain pump.
U.S. Pat. No. 3,457,929, assigned to the assignee of the present invention, discloses a dishwasher which, in the modified form shown in FIG. 2, includes a spray pump which circulates dishwashing liquid from sump to the tub. Liquid returns to the sump to be recirculated through a foraminous wall, with food particles retained in a funnel to be pumped out at the end of a wash cycle by a drain pump.
Dishwashers having fluid handling systems including sumps for collection of water draining from the wash cavity are well known in the prior art. A typical fluid handling system includes a single wash pump which operates in a sump to recirculate water within the wash cavity ('359 noted above), or a single pump which operates to recirculate water within the wash cavity and to pump water out of the sump ('680 noted above). Another handling system includes a pump which operates in a sump to recirculate water within the wash cavity, and a drain pump which operates in the same sump to pump water out of this sump ('929 noted above).
A disadvantage of such systems is that they are incapable of operating on separate sumps which receive water from the wash cavity and which contain wash or rinse water in various states of filtration. Among further disadvantages, particularly to a fluid handling systems using a single pump, is the use of a pump of unnecessarily high capacity to drain the sump, which wastes energy and requires additional expense to provide either the controls or valves necessary to provide both a wash and a drain function.
Yet another fluid handling system ('666 noted above) includes a wash pump which operates in a sump to provide wash water to a spray arm for distribution in the wash cavity, and a rinse pump which operates in a sump to provide rinse water to a spray pipe for distribution in a wash cavity. All water draining from the wash cavity enters the wash pump sump whereupon, when the water reaches a given level in the sump, a siphon tube drains the water from the wash pump sump. A disadvantage of such a system is that the wash pump sump is not drainable to a water level higher than that in the wash pump sump. Furthermore, draining is less controllable than with a drain pump, since it is a function of water height in the wash sump pump rather than a switchable drain pump.